A technique for extracting gravity anomalies originating from sediments deposited on folded oceanic crust

Abstract

Negative gravity anomalies observed over sediments accumulated on folded oceanic crust are usually caused by two negative density contrasts. The first is the contrast between low-density sediments lying on folded high density oceanic crust and the second is the contrast between low-density oceanic crust immersed into the high-density upper mantle. Because the anomaly is caused by two regions with different densities, modeling it is not straightforward. Most standard methods only allow for modeling bodies with a single density contrast. This paper describes a Fourier technique to separate the anomaly caused by the sediment distribution facilitating its modeling using a standard method. It is assumed that the oceanic crust over the region under consideration has a constant thickness and that the densities of sediments, oceanic crust, and upper mantle are constant. The technique was tested with artificially generated negative gravity anomalies for a hypothetical case and found to work satisfactorily. Even though the two-dimensional version of the technique is described here for the sake of convenience, it can readily be extended to the three-dimensional case.